I used it to adjust the hard nail of the lathe. The price is not high so far, but compared with cheap (100 level level), it was the difference of clouds! I was lost at a price similar to that of the monotaro brand, but I chose this because there was "inner grinding" in the explanation text. I actually tried using it, but since I bumped it and hit it I think I will purchase it again. (It is a waste as the diamond section is still living ...)